There used to be guidelines many moons ago, but i cant remember what they were, and they are irrelevant now anyway.
When you construct a ring (or any other circuit), you need to consider the loading, so if you were to install a ring into 4 bedrooms, and put 4 twin outlets in each room, and SFCU for a boiler or whatever, you wont have problem with loading, no matter how many tellys, laptops etc etc gets plugged in, you will not exceed the cable rating. But put a kitchen, utility room, garage on one circuit with unlimited outlets than you may encounter problems.
It all comes down to using a bit of common sense, and looking at the info available to you. If you look in the electricians guide to the building regs, there are guidelines as to how many outlets you should provide in each location, but they are only guidelines. You need to consider inconvenience in the event of a fault, so would it be a good idea to shove a 125m ring in? i doubt it, cos all the sockets might go off at once. You are correct in your assumption that you can have unlimited sockets on a ring, you can on a radial as well, but it all comes down to common sense. You can also spur from each unlimited socket once. When you design and construct any circuit, you need to ensure compliance to the regs, so think about Zs values and volt drop when calculating the length.
Cheers..........Howard
